1. Field of the Invention
The present invention relates to a technical field of spherical aberration correcting method and apparatus in a recording system for recording bits of information onto an optical recording medium.
2. Description of the Related Art
It is general that a transparent layer is formed on a recording surface of an optical disk serving as an optical recording medium. The transparent layer has a predetermined thickness and is placed to cover the recording surface of the optical disk so that the recording surface can be protected.
An optical information recording/reproducing system is configured to irradiate a reading or recording optical beam onto the recording surface of the optical disk through the transparent layer to read or record data from or to the optical disk.
However, in reality, it is difficult to form the optical disk so that each portion of the transport layer falls within a specified range of thickness. As a result, a usual optical disk has as much a thickness error as several tens of micro-meter (μm) due to irregularities over the transparent layer. Such an error in the thickness of the optical disk causes spherical aberration to occur in an optical beam irradiated onto the optical disk, thus reducing accuracy of reading or recording data from or to the optical disk.
For actually recording bits of information onto the optical disk, changes in recording conditions including the circumferential temperature at the start of recording and the like will cause the spherical aberration to fluctuate.
The more accelerated the rate of recording is in the future, the more influenced the spherical aberration to a recording characteristic will be, so that it is necessary to prevent the spherical aberration as much as possible. The foregoing problem, though it is mere one example, is included in the difficulties which should be solved by the present invention.